Here in the U.S., especially the southern states, ham hocks are the ankles of pigs that have been hickory smoked. The skin is still on, but there's little fat. The smoke cure gives a unique taste that works well in many dishes, but, traditionally, they're used in bean dishes served with cornbread as a side...
In the area of the south in which I grew up with grandparents, there were many German people and they called the same cut "knuckles" so I suspect your "pork knuckles" are corret...